Feels like we need a new production bonus resource that doesn't give anything else.Very detailed indeed. I didn't suggest changing anything about resources around capitals since they looked fine.
Replacing the starting iron with a starting stone is risky, since it gives an edge to wonder building and it allows the stone building that trades production. If you know there's always some stone around, that can change the starting decisions very strongly. But you wouldn't rush iron only for a small iron deposit, would you?
Still, stone is only given to starts with low production so the 10% shouldn't matter that much. And it's already given to heavy grassland starts, regardless of those grasslands being hills/forest or not.